Thin film processing apparatus



THIN FILM PROCESSING APPARATUS Filed Dec. :21, 1966 INVENTORS JAMES DONOVAN BY MAX MENDELSOHN AITORNEY J. DOI\IIOQVAYN ET AL 3,346,034

United States Patent ABSTRACT OF THE DISCLOSURE A rotary, horizontal, thin-film type evaporator containing a damming device occupying only a segmental portion of the vapor area between the processing and vapor sections of the evaporator to prevent material from entering the vapor sections, and to avoid excessive pressure drop. A crescent-shaped or chordal-shaped, fiat damming barrier between sections is provided by the use of a fiat ring shaped or flat, straight material inserted in the flanges between such sections thereby providing rapid adjustment and flexibility.

Background 0] the invention Our invention relates to a rotary, thin-film type fluid processing apparatus for the treatment, reaction or processing of liquids. In particular, our invention concerns a wiped or turbulent, thin-film evaporator which includes damming means to prevent or inhibit the significant flow of liquid material from the processing chamber into the vapor chamber of the evaporator without excessive pressure drop between the chambers.

In those horizontal or inclined-axised, thin-film type apparatus such as evaporators, it is often most desirable to prevent or inhibit the flow of liquid material processed through the evaporator from entering or accumulating into the vapor chamber of the apparatus. In the past, various means have been suggested to segregate the vapor chamber from the processing section of the thin-film evaporator in order to prevent the flow of material either at the feed or product end of horizontal or inclinedaxised evaporators from flowing into the adjacent vapor chamber(s) or to prevent splashing of the material from the processing section into the vapor chamber. In addition, various means have been provided to recover and return the condensates and other material splashed back from the vapor chamber back to the processing section or to the product outlet.

For example, an annular dam has been suggested between the processing and vapor chamber sections, which dam includes an annular ring secured between the sections (see US. Patent No. 3,261,291 and No. 3,228,453). Such an arrangement is not fully satisfactory, since such a dam constricts the cross sectional area of the vapor path, and often creates a significant pressure drop between the processing and vapor chamber sections. In addition, such dams create problems in'the special contouring of the evaporator body, and in the manufacturing operation such as in additional welding or other operations, which increases the cost of the evaporator. Such dams as have been suggested in the past are relatively inflexible in design and operating characteristics and often must be designed into an evaporator for each particular operation.

Summary of the invention We have discovered that an effective and significantly unexpected result in the operation of mechanically-aided, thin-film evaporators may be achieved by employing damming means which are non-annularand occupy a selected segment of the vapor flow area between the processing and vapor chambers. Our improved damming devices are often effective to retain percent or more of the liquid flows that would enter the vapor chamber under typical conditions, while avoiding excessive pressure drop. In particular, we have found that a crescent or chordal type arcuate segment that does not extend generally beyond about in effective position in the vapor flow path between the process chamber and the vapor chamber provides for a progressive increase in damming action. Such an arrangement avoids many of the disadvantages of the prior art in that the vapor flow at the higher segment of the apparatus is not inhibited, as would be the case with a continuous annular dam between the sections. Furthermore, the pressure drop due to the restriction of the across-sectional area is also considerably diminished, while our dam being located at the lowest point of the evaporator serves as an eifective obstruction at the low point and creates a liquid head which the liquid in the processing section must overcome. We have also provided means whereby a particular shape and location of the damming means in the lower segment may be varied in a simple operation in order that an evaporator may be employed with-out the damming means or with progressively different damming means, thereby providing a flexible, thin-film type processing apparatus. Our damming means in particular cases may be adjustable to a particular crescent shape on one or the other side of the lower 180 segment of the vapor path to operate in those cases Where there is a particular change in vapor paths or vapor path location in any particular unit or in a typical operation in the lower portion of the vapor path. Such a damming means also reduces and controls the pressure drop between the sections to a minimum, and, therefore, has a considerable functional advantage over prior art devices.

Accordingly, it is an object of our invention to provide an improved, thin-film apparatus such as an evaporator characterized by damming means separating the processing and vapor chamber sections of the apparatus wherein pressure drop between sections may be minimized.

Another object of our invention is to provide a rotary, thin-film type evaporator of a substantially horizontalinclined type characterized by a crescent shaped or chordal shape damming bafiie between the processing and vapor chambers, which provides significant advantages over the prior practices of employing an annular, continuous type ring between such processing and vapor chamber sections.

A further object of our invention is to provide a thin- -filn1 type evaporator having a crescent or chordal shaped damming baffle between the processing and vapor chamber sections, which baflie may be readily adjusted or positioned to provide operating flexibility to the evaporator.

These and other objects of our invention will be apparent to those persons skilled in the art from the accompanying drawing and the following, more detailed description of our invention wherein:

Brief description of the drawing FIG. 1 is a schematic, longitudinal section through a cylindrical, rotary wiped, thin-film evaporator of our invention employing a particular damming baffle;

FIG. 2 is a cross-sectional view of the evaporator of FIG. 1 along lines 2-2;

FIG. 3 is a cross-sectional view of another modification of ourinvention in which a chordal type bafile is used.

FIG. 4 is a cross-sectional view of the evaporator show,- ing another embodiment of our invention.

Description of the preferred emb0diment(s) Briefly, our invention comprises in combination an evaporator which has a closed chamber as a processing section having an interior wall, a rotor within the chamber, means to rotate the rotor, generally radially and axially extending rotor blades on the rotor, which blades extend from the axis into a close, generally uniform, thinfilrn forming association with the interior wall of the chamber, a feed inlet into the closed chamber, a product outlet out of the closed chamber, a vapor chamber adjacent and in fluid flow communication with the rotor containing portion of said chamber, a vapor outlet in the vapor chamber for the withdrawal of vapor therefrom, a liquid outlet in the vapor chamber to remove excess liquids, and means dividing the vapor chamber from the processing section of the apparatus, which means includes a darn or baffle. The baffle means comprises nonannular baffles which occupy only a segmental portion of the vapor flow path cross-sectional area between the sections and preferably the lower 180 segment. Preferred embodiments of our invention include the use of a crescent shaped or chordal shaped type baflle generally of variable height and shape between the processing and vapor chamber sections and generally located in the lower 180 segment between the sections. The baffle element is generally of suflicient height to create a slight positive liquid gravity head for the liquid collected in the vapor chamber, and to provide a minimum pressure drop in the restricted vapor flow area between the processing section and the vapor chamber.

We have discovered that during the operation of a thin film type processing unit a significant portion of liquid transfer occurs at the lower segment of the evaporator and therefore, that a damming baflle occupying only a small portion of the cross-sectional area at the lower segment of the evaporator between the processing section and the vapor chamber section is significantly and unexpectedly effective in reducing or preventing the collection of condensate and liquid material in the vapor chamber. Furthermore, we have found that a damming bafiie located especially in the lower segment between the processing section and the vapor chamber creates a slight liquid gravity head from material so collected thereby enhancing the operation of the thin-film processing unit, and that only a minimal pressure drop occurs between the processing section and the vapor chamber section.

Our damming baffle may be of any size and shape located between the processing section and the vapor chamber either at the feed or product end of the evaporator. The particular location or shape of the nonannular damming section employed in accordance with our invention may be varied depending upon the particular operation and the operational problems in connection herewith.

The crescent shaped damming baflle is advantageous in providing a smooth and gradually progressive dam between the sections, and in one embodiment is readily adapted so that the crescent dam area may be extended to one or the other side of the vapor flow path as required, or readily removed or positioned or rendered essentially non-operational where a damming means is not needed.

Our invention will be described in connection with a horiZontal-axised, rotary, wiped, thin-film type evaporator wherein a vapor is generated during the processing operation following the same direction as the product, i.e., concurrent with respect to the feed material. Of course, our invention may also be employed in those evaporators wherein the flow of the vapor to the liquid feed is counter-current, as well as in conical type evaporators having, for example, a larger diameter at the feed end than at the product end (see US. Patent 2,927,634).

FIG. 1 shows a horiZontal-axised, cylindrical type evaporator 10, comprising a closed, cylindrical chamber 12 having interior walls and surrounded to all or part of its length by a temperature control jacket 14, which is adapted for the introduction of a heating or cooling heat exchange fluid such as steam, cold water, or the like. Chamber 12 is further characterized by a feed inlet 46 i for the introduction by pump, gravity or vacuum of a feed material to be processed through the evaporator,.a product outlet 18 at the opposite end thereof for the removal of the product material, and a vapor outlet 20, which vapor outlet extends into a vapor chamber 22 adjacent the product end of the evaporator 10. Closing heads 24 and 26 are secured to either end of the chamber 12, and support a horizontally-inclined, central-axised, tube-like rotor 28, which extends from the one end to the other end of the chamber 12, and through the vapor chamber 22. The rotor 28 is driven by a motor or other means (not shown) and generally extends outwardly from each end of the closing heads. The rotor 28 extends through suitable bearings 30 and 32, and seals or packing material 34 and 36 are disposed at either end of the evaporator 10. Extending axially outward from the rotor shaft 28 are a plurality of four or more radial rotor blades 38, the blade tips of which extend into a small, but generally uniform, closely-spaced relationship with respect to the interior wall of the chamber 12, so that upon rotation of the rotor shaft 28, the rotor blades 38 provide a thin, wiped or turbulent film of the processed material on the heated interior wall of the chamber 12.

At the bottom of the vapor chamber 22 is a drain outlet 68 for removing accumulated liquid from the vapor chamber. Located slightly beyond the product outlet 18 in the direction of the fluid flow, and securing the closed processing chamber 18 the vapor chamber 22 is a flange 40 circumferentially surrounding the evaporator 10 which flange is comprised of lips 42 and 44. The lips are characterized by a plurality of openings 46 in which bolts or other fastening devices are attached. Within the lips of the flange 40 is placed a flat ring shaped damming element 48. This ring shaped damming element 48 has an inside diameter which is equal to or greater than the inside diameter of the cross sectional area between the closed processing chamber and the vapor chamber. The outer diameter of the ring shaped element extends into the flange to a point about halfway between the inside diameter of the closed chamber, and the outside diameter of the flange bolts. The ring element may be adjusted within these limits to provide damming arrangements of various arcuate lengths and heights by loosening the bolts on the flange 40 and moving the ring element 48 to the desired position. The ring shaped element may be positioned to eliminate any damming arrangement if desired. When the desired damming arrangement is reached the bolts are secured, locking the ring shaped element into position. Of course, it is understood that the flat ring type element may have slotted openings or holes if desired which openings would be aligned with the bolts in the flange to provide the desired flexibility in adjusting the ring shaped element to provide the proper damming arrangement.

The preferred damming arrangement of the ring shaped element 48 as shown by the solid line in FIG. 2 has its greatest height at the point where the majority of liquid material passes int-o the vapor chamber. The height of the damming element 48 progressively tapers off until it reaches either side of the interior wall, thus, forming an arcuate dam which inhibits or prevents a majority of liquid material from entering the vapor chamber. A progressive damming arrangement of this type wholly contained in the lower degree segment of the vapor flow path minimizes to a great extent the pressure drop between the closed processing chamber 18 and the vapor chamber 22 which is normally found in annular damming devices and the vapor flow at the higher segment of the evaporator passes through uninhibited.

Other damming arrangements are shown by the dotted lines 50-52 in FIG. 2, where the ring shaped damming device is positioned to the one side or the other as shown in the vapor flow path between the closed processing chamber and the vapor chamber.

In the operation of my evaporator 10 referring to FIGS. 1 and 2, a material such as a low viscosity liquid to be processed through the evaporator is introduced into the feed port 46 by pump, gravity or under vacuum while the relatively non-volatile product material is withdrawn through the product outlet 18, and the vaporized material withdrawn through the vapor outlet 20. Of course, if desired, other vapor product outlets and feed inlets may be used. The rotor shaft 28 and the rotor blades 38 are rotated at high speed during the processing to form a thin film of the feed material against the interior wall of the chamber 12 with a heat exchange fluid such as steam introduced into the temperature control jacket 14, whereby the thin film on the interior wall is placed in heat exchange relationship with the steam in the heating jacket to effect an evaporation of the relatively volatile component of the feed material as the material processes through the evaporator.

When the material is processed the vapor rises to the top of the evaporator and the viscous or liquid material gravitates to the bottom of the evaporator and out the product outlet 18. However, some of the liquid material becomes entrained in the vapors and passes into the vapor chamber or is splashed into and accumulates in the vapor chamber. The problem of entrainment is magnified by the whirling action of the blades in that liquid that would normally condense out of the liquid-vapor mixture is retained by the centrifugal action of the blades. However, about 90% of the liquid material that enters the vapor chamber passes through the lower 180 degree segment of the cross-sectional area dividing the processing chamber 12 from the vapor chamber 22.

The damming element 48 is so designed so that if no damming action is required the inner circumference of the damming element is flush with the inner circumference of the chamber 12. The outer circumference of this damming device extends about halfway between the inner circumference of the flange 40 and the outer diameter of the flange bolts. In an operation where the damming action is required the damming element is adjusted by removing or loosening the fastening devices securing the damming element in the flange. The desired setting may be reached by moving the flat ring type damming element upward and/or side to side as shown in FIG. 2, then the fastening devices are tightened securing the damming element in the desired position. In this manner, an arcuate dam of any desired length and height may be positioned in the lower 180 segment of the vapor flow path to prevent or inhibit the fluid flow of liquid materials that would normally enter the vapor chamber. This is accomplished without any significant pressure drop occurring between the closed processing chamber and the vapor chamber and further this progressive damming action allows the vapor flow to pass through the upper section of the evaporator uninhibited which advantages are not found in annular type damming devices.

Another embodiment of our invention as shown in FIG. 3 is to place a chordal type damming element 54 in the lower 180 segment of the flange. This damming element may be raised straight up and/or side to side depending upon the height and length desired for the particular damming operation as shown by the dotted lines 56 and 58 in FIG. 3. This arrangement has the same advantages i.e. minimum pressure drop between the chambers and uninhibited vapor flow through the upper section of the evaporator as the arcuate shaped damming element.

A further embodiment of my invention is shown in FIG. 4, where a fixed support element 60 extends across the lower 180 segment of the evaporator which support element is characterized by slotted holes 62 at either end thereof. A chordal type darn element 66 is affixed to the support element 60 by bolts 64 or other means which bolts are aligned with the slotted openings 62 in the support element. This embodiment provides a flexible chordal type damming element in which the dam height may be adjusted for the particular operation. Of course, it is understood that a concave or convex damming element may be used in lieu of the flat chordal element as shown.

Our invention as illustrated and described avoids many of the difiiculties associated in the past with damming devices used in thin film apparatus and provides significantly improved and efficient results in which the flow of liquids are prevented or inhibited from entering the vapor chamber.

We have now developed a new and unique apparatus and method for preventing or inhibiting the accumulation of liquid material in the vapor chamber of a horizontal inclined thin film type evaporator and, therefore,

What we claim is:

1. An improved fluid processing apparatus of a rotary, horizontal or inclined thin-film type which comprises in combination:

(a) a closed chamber characterized. by an interior wall defining a surface of revolution;

(b) a rotor within a portion of the chamber;

(c) means to rotate the rotor;

(d) rotor blades secured to the rotor for rotation therewith, the blades generally, radially and axially arranged from the rotor and extending into a close relationship with the interior walls;

(e) an inlet in the chamber for the introduction of feed material to be processed;

'(f) a product outlet in the rotor containing portion of the chamber spaced apart from the inlet for removal of processed material from the chamber;

(g) a vapor chamber in the closed chamber and adjacent one end of the rotor containing portion of the chamber;

(h) a vapor outlet in the vapor chamber for the removal of vapors;

(i) a liquid outlet in the vapor chamber for the removal of liquids;

(j) a damming means secured to the wall of the chamber between the rotor containing chamber and the vapor chamber which means comprise a non-annular segmental dam element positioned at least in part in the lower degree portion of the vapor flow path between the closed chamber and the vapor chamber, the height and shape so selected as to prevent, in part, processed material from entering the vapor chamber and to minimize the pressure drop.

2. The apparatus of claim 1 wherein the damming means includes a chordal shaped dam element.

3. The apparatus of claim 1 wherein the damming element includes an arcuate shaped darn element.

4. The apparatus of claim 3 wherein the arcuate element has its greatest height in the lower portion of the vapor flow path.

5. The apparatus of claim 3 wherein the damming means includes a flat ring element such element having an inside diameter substantially the same as or greater than the vapor flow path diameter, and which may be positioned in the vapor flow path to provide an arcuate shaped segmented dam element of desired shape, height and location.

6. The apparatus of claim 3 wherein the evaporator includes flange means to secure the vapor chamber to the rotor containing chamber and to secure the flat ring dam element in position between the flange means in a manner so that it is adjustable to provide an arcuate shaped damming element or no restriction in the vapor flow path.

7. The apparatus of claim 1 wherein the damming means includes a fixed support element; a chordal dam element and means to secure the dam element to the support element in an adjustable manner.

No references cited.

WILBUR L. BAS'COMB, JR., Primary Examiner. J. 'SOFER, Assistant Examiner. 

1. AN IMPROVED FLUID PROCESSING APPARATUS OF A ROTARY, HORIZONTAL OR INCLINED THIN-FILM TYPE WHICH COMPRISES IN COMBINATION: (A) A CLOSED CHAMBER CHARACTERIZED BY AN INTERIOR WALL DEFINING A SURFACE OF REVOLUTION; (B) A ROTOR WITHIN A PORTION OF THE CHAMBER; (C) MEANS TO ROTATE THE ROTOR; (D) ROTOR BLADES SECURED TO THE ROTOR FOR ROTATION THEREWITH, THE BLADES GENERALLY, RADIALLY AND AXIALLY ARRANGED FROM THE ROTOR AND EXTENDING INTO A CLOSE RELATIONSHIP WITH THE INTERIOR WALLS; (E) AN INLET IN THE CHAMBER FOR THE INTRODUCTION OF FEED MATERIAL TO BE PROCESSED; (F) A PRODUCT OUTLET IN THE ROTOR CONTAINING PORTION OF THE CHAMBER SPACED APART FROM THE INLET FOR REMOVAL OF PROCESSED MATERIAL FROM THE CHAMBER; (G) A VAPOR CHAMBER IN THE CLOSED CHAMBER AND ADJACENT ONE END OF THE ROTOR CONTAINING PORTION OF THE CHAMBER; 